2400 baud can be very slow for transfering large files.Modems advertised as 4800 are really only 2400 with data compression suchas MNP-5 or even just software data compression. Don't be fooled.A 9600 or faster modem will make a tremendous difference on your transfer time.Most 9600 Baud users never want to go back to 2400. There is a lot of confusionand mis-information about 9600 Baud and faster Modems. I wrote this to helpclarify and point out the differences between the different modems availablefor MS-DOS machines.

If price is no object, the Best modem to get for BBS use is the USRoboticsDual Standard. It is a combination of the HST 14400 Baud modem and aV.32/V.42 modem all rolled into one modem.

If price is an Issue, (like it is to most people) then you may want to considera Standard HST 14.4k, or a different Brand if that is also too expensive.But if you do not buy a USRobotics Modem, you will not be able to hook up toa Standard USR HST 14.4k, which is the most Common BBS Modem.

Other then USR, you could get a V.32 or V.32/V.42 compatable modem for about 25% less then a Standard HST, or you could get a 9600 FAX/Modem for less thenhalf the cost of a V.32 See the price comparisons at the end.

This information was obtained from several reputable sources, but noneof it is guaranteed to be 100% accurate. I am not responsible for anyincorrect information in this document, nor am I responsible for anyloss of profits to anyone resulting from reading the information in thisdocumentation. Proceed at your own risk.

Since new modem brands, models, and new prices are appearing constantly,this documentation is going to need a lot of updating. Also some of the CurrentInformation may need corrections as well. You are welcome to make changes tothis information, but please send me a copy of your update so that I can addyour changes to the current latest version I have. That way all the correctionsthat are made will be added to the latest version, which will also be avail.for download on my bbs.

At one Time Hayes was the standard in modems. All other modems tryed to be "Hayes Compatible". This is still true with 1200 and 2400 bps modems,but NOT when it comes to 9600 or faster modems. Hayes established a Standardcalled the AT command set. Other modem manufacturers quickly adopted thisstandard and the AT commands are still used today (with a few commands added).

Well Along Came USRobotics, and designed the HST, a proprietary 9600 modemthat quickly became popular, and no one else was allowed to duplicate. Hayes then also came out with a proprietary 9600 modem, but since it could nottalk to the HST at 9600 it never became popular in the IBM world.Next USR improved their HST modem, making it transfer at 14400 bps withouteven using data compression. USR's HST became the standard for MS-DOS compatable High Speed modems.

Realizing that the industry needed a "non-proprietary" 9600 standard thatany manufacturer could use, the CCITT came up with the V.32 specification.It took a several years before modem manufactures started finding ways toimplement this standard at a price competitive to HST, but a few manufacturesstarted producing them, including Hayes. Next the CCITT relized that bettererror correction and data compression methods existed, and thus came up withthe V.42 and .V42 bis standard. They are currently finalizing the V.32bisspecification, which will also run at 14,000 Baud in full duplex.

Now Modem Manufactures all seem to be jumping on the V.32 Bandwagon,Even USR offers V.32/V.42 modems and allows the HST's to be upgraded toa "Dual-Standard" so it can be both HST and V.32/V.42 in one.The New HSTs also have V.42bis and can be upgraded to the new V.32bis DS.The price Difference between the HST and the HST-DS is considerable though,which is why Most BBS Sysops still buy the HST without the "DS" option.The V.32/V.42 have become the standard in the Macintosh world, and someMS-DOS BBS's are now running V.32/V.42 instead of supporting the HST,and some are supporting both types, using multiple lines.

Fax Machines have had their own standards, CCITT V.27, V.27ter, and V.29define the modulation scheme used for Fax, and T.30 defines a Fax Protocol. Fax Machines nowdays can transfer Faxs at 4800 or 9600 Baud. Most Fax/Modemscan only transfer files at 2400 Baud. There is now one Fax/Modem which canalso transfer files at 9600 bps, and is far less expensive then the V.32/V.42s,plus offer the benefits of a Fax machine.

The International Consultive Committee for Telegraph and Telephone (CCITT)set the V.32, V.42, and V.42bis Standards in 9600 bps communications.They have also set the standards of 1200 and 2400 bps in Europe.Unfortuntly the V.32 standard is very expensive to implement for themodem manufactures, and the HST has already become the industry standardin the IBM BBS world. But since any company may manufacture V.32/42 Modemswithout a licence or royalty, there is more price-competition going onwith these then with the HST, which currently has no true competition.

Half-Duplex is When Data is Transmited in one Direction at a time.Full-Duplex is both directions at once. 2400 buad modems are Full-Duplex.The HST Modem uses an improved form of Half-Duplex, in which one direction istransfering at high speed while the other direction is sending ACK/NAK signalsat a slower speed. A simular method is used on the Speedmodem.

V.32 modems use Full duplex, which in most cases does not improve performancewhen used on a BBS. There is one way to take full advantage of a Full-DuplexModem: By using a protocol called Bimodem to upload and Download as the sametime at 9600 bps in each direction! Unfortunately Bimodem has not become verypopular. Most BBS's and users still use one direction transfer protocols suchas Zmodem or YModem-G.

MNP (Microcomm Network Protocol) levels 1-4 are methods of error correctionin which the two modems connected verify the integrity of the data transmitted.Error correction is required for several streaming protocols such as Ymodem-Gin which the protocol sends a constant stream of data and lets the modems dothe error correction. This requires a clean, noise free line as streamingprotocols will abort if line noise interferes too much.These MNP Levels are used in almost all High Speed Modems Made today, ButJust because two modems both have MNP it does not ensure that they will bothtalk to each other (at over 2400 baud).

MNP Level 5 is for data compression. Since All BBS's have their files archivedin ZIP, LZH, GIF or some such compressed format (try to ZIP a LZH file), MNP5can actually increase the overhead by attempting to compress the file further.Therefore BBS's leave MNP5 turned off, and so should the BBS callers.

HST stands for "High Speed Technology" - a method of communicating at highspeeds whech was developed by US Robotics in 1984. HST is a proprietarymethod so currently only US Robotics is allowed to Make HST Compatible Modems.The original HST modems were 9600 bps by using a 9200 bps channel in onedirection and a 450 bps "back channel" in the other to send ACK/NAKsignals for confirmation of data - a half duplex mode - often referred toas "ping-ponging". In 1989 USR improved the HST to run at 14400 bps by furtheroptimizing their proprietary method. All HST's sold now include the 144kspeed as well as the original 9600 mode. Because the HST 14.4k is a raw speed,It allows the HST to transfer pre compressed files such as ZIPs at fasterspeeds then any other 9600 modem: over 1700 Characters per second.

The HST has become the "BBS-Standard" in high-Speed Modems. More BBS's usethe HST then any othe type of modem, including the V.32.

As of January 1st 1991 all HST modems also include the V.42/V.42bis errorcorrection and data compression (not to be confused with V.32).

The HST's can also be upgraded to the HST "Dual Standard" allowing it to alsobe V.32bis compatable. The price is significant for this upgrade however,and in very few cases is any speed gained.

V.32 is a 9600 Baud standard that was established by the CCITT back in 1984. V.32 is full duplex (9600 bps in both directions at once). Normally this wouldbe impossible, but using a technique called "echo cancellation", one modemcan filter its own tones from the phone line, enabling it to pick out thesignals from the other modem. However, echo cancellation requires that highspeed modems include built-in digital signal processor (DSP) chips, which isthe main reason V.32 and V.42 costs so much. V.32 also includes a fallback to 4800, if line noise becomes a problem at 9600.The V.32 standard also provides an optional error-reduction sceme, called"trellis-coded modulation (TCM). TCM allows 9600 modems to check fortransmision errors with a redundancy bit, which results in fewer errors onnoisy lines. Most V.32's include this option, but some do not.

It was first realized in 1989 that it is feasible to push V.32 up to 14,400baud, the same speed as the HST now runs. This requires even better echocancellers and an overall improvment in reciver quality, so it will be more costly to produthen the V.32 to produce. V.32bis has not yet officially beenfinalized CCITT, but as of January 1st US Robotics has started shippinga new version of their Dual Standard Modem which includes V.32bis in an earlybut functional form. USR plans to update their DS ROMS when the CCITT actuallyrelease the completed V.32bis specification, scheduled for mid 1991.It's expected that other Modem manufacturers will not be able to offer theV.32bis technology untill the 4th quarter of 1991.

V.42 is nothing to do with actual modem speed, but how how the error correctionand data compression schemes interface. When the CCITT approved V.42 in 1988,they desided to include two differnt error correction and data compressionschemes. The first one is MNP,(short for Microcom Networking Protocol).MNP classes 2, 3, & 4 which handle error correction. Note that MNP-5 was notincluded in the V.42 standard because it is only used for data compression.MNP was made an offical standard due to the large number of modems thatcurrently use it. The Second method is the prefered method, known as LAP-M(Link Access Protocol-Modem). A modem with only MNP is called "V.42 Compatible"and one with LAP-M its known as "V.42 Compliant". If a V.42 Compliant connectedto a V.42 compatible, it would first try to Handshake with LAP-M, and after itrelized that the othe modem is not Compliant, it would try the MNP Method, andthey connect.

Most V.42 modems are fully V.32 compatable, but they do NOT have to be,according to CCITT guidelines. So when purchasing a V.42, make sure thatit is really a V.32 Modem that is also V.42 complient or compatable.There are now some 2400 baud modems which are also V.42bis compliant,so since the LAP-M gives 4:1 data compression they are advertised as"9600 throughput", which really can be misleading and confusing.

V.42bis is a new CCITT standard for data compression techniques, which wasappoved in late 1989. To Support V.42bis, a modem MUST support both LAP-M andMNP-5, unlike the Standard V.42 in which LAP-M is only an option. V.42 providesa maximum data compression of 4:1, giving a 9600 bps modem a throughput up to38400 bps. MNP only offers 2:1 Compression. Like MNP-5, LAP-M and V.42bis willnot be effective when transfering compressed files from BBS's, such as ZIPfiles. Since V.42 is implemented in firmware, many V.42 complient modems canbe upgraded to V.42bis with a new ROM.

A less expensive method of 9600 bps communication can be achieved withoutusing the CCITTs method of "echo cancellation", so that the a digital signalprocessor is not needed, making the cost much less expensive.This method is used on the Compucom Speedmodem. The Speedmodem also usesDynamic Impedance Stabilization (DIS) to increase the relability of thetelephone interfaces signal-to-noise ratio of the telephone line by increasingthe clarity and power of the signal, and automatically compensating forimpedence variations on the phone line. This reduces the probibility ofline noise, allowing the Protocols to transfer files with less overheadIt also has a faster fallback rate of 7200 bps if too much line noise existsfor 9600 communications. This makes the Speedmodem stand up to worse linenoise conditions at a faster rate then V.32 can handle.The Speedmodem is also a 9600 bps Group III Facsimile, so with this modem,you can send document and scanned images as a Fax, as well as recive Faxs.It supports BitFAX by Bitcom and any other 3rd party FAX software which uses the standard CCITT AT-FAX command set.A Data Compression called CSP (CompuCom Speed Protocol) is used to yeld acompression of up to 4:1, giving a throughput of up to 38400 bps.This however, like MNP5 will not be effective when transfering compressedfiles from BBS's, such as ZIP files.

DIS and CPS are proprietary methods owned by CompuCom, Sunnyvale, CA.Because this modem is inexpensive more people can afford to buy it, and sinceits both a FAX and a Modem in one, it should gain popularity quickly. It is still a new product, but hundreds of BBS's are showing support for it.

----------------------------------------------------------------------------- What Next?

By mid 1991 the V.32bis standard will be finialized, and by that years endthe several 14,400 Bps full duplex modems will be on the market.There is already talk of the CCITT releasing another standard in 1992,which will be for 192,000 bps. Since these modems are expected to costconsideribly more then the V.32s currently on the market, they will beout of the price range of most BBS users.

You'll see ads claiming that you can attain 19,200 bps or 38,400 bpswith a 9600 Baud modem - this is true only if you are using MNP5 or otherform of data compression on an uncompressed data or text file. Any 9600 Baudmodem using compression will transfer at that effective rate. But for BBS use, where files are already compressed (such as ZIPs, LZHs, GIFs)MNP5 will actually slow down throughput by attempting to compress a file thatis already compressed. Generally when using a modem for BBS transfers, itsthe RAW speed of the Modem and not the throughput which is important.

Figures of around 1700 cps by the HST modems are attained through proprietarymethods not available on other modems.

CONFIGURABILITY:================In High Speed Modems, there is a lot more to configure than on a 2400 Baudmodem. Be sure your modem comes with NRAM (Non-volatile Random Access Memory)that can store your modem configuration, making long init strings unnessesary.Also many modems have dip switches to set the default configuration, whichalso simplys things. If you buy an Internal Modem, be sure its fullyConfigurable as far as selecting the com port and IRQ (interupt request)setting. Some modems can be addressed from Com1: up to COM8:

UARTS=====Internal Modems have a serial port built in, and External Modems use anexisting Serial Port in the computer. A serial port has a UART chip to bufferand control the Input/Output (I/O). The XT usually has an 8450 UART which willhandle up to 9600 Baud. The AT usually has the 16450. If you have an externalmodem you should replace your UART with the 16550 (NS16550AN).

INTERNAL or EXTERNAL====================MS-DOS Users can choose internal modems, that plug in a computers slot,or external, which plugs into an existing serial port with a serial cable.Internals are usually less expensive, take up less space, have the correct UARTalready installed (see below) and don't need a cable. But the Externals usuallyhave a lot of little lights on it that you can stare at, and its easier to moveto another machine. So which ever you prefer (or is available in some cases).

If Considering a USRobotics Modem=================================You only need to worry about weather you want the HST(which can be upgraded later), or the Dual Standardwhich is the same modem with the V.32bis option included.

If Considering a V.32/V.42 Modem========================================Some questions to ask:

Can you afford the USR "DS" instead?Is it both V.32 and V.42 compatible?Is it V.42 compatible, V.42 compliant, or V.42bis?If its not V.42bis or compliant, can it be upgraded?Do Local/National BBS's support it?Would you rather wait a year for a V.32bis?What is the warranty? 5 years?

If Considering a FAX/Modem==============================some questions to ask:

Is it Send and Recive Fax?Does it support 3rd party FAX software?Is it 4800 or 9600 bps?Does it support MNP?Does it support other compression?Do Local/National BBS's support it?What is the Warranty? 5 Years?

These modems will usually be downwardly compatible with 2400 Baud and slowermodems, Which means they are also CITTY V.22bis and Bell 103/212A compatible.Most have an auto-fallback mode that will detect the highest negotiable Baudrate, which can either through hardware or software configuration. If the modem is V.42 capable, it will fall back to MNP if the other modem isnot LAP-M capable, but is MNP capable. Modems supporting MNP will connectwith data compression/error correction with other MNP modems at the highestBaud rate negotiable between the two. The speeds listed here are the actualRaw speed, not possible throughput that can be achieved using data compression.

Listed in alphabetical order by brand name -

Generic V.32 only Made by a number of companies using the CCITT method of communicating at 9600 bps. These are expected to become outdated as V.42 is added to most V.32 modems - Talks to other brand V.32 modems at 9600 Baud.

Generic V.42 Only If a Modem is V.42 or V.42bis only, and not V.32, then it can only talk to other V.42 modems at 2400, (with 9600 throughput using data compression) This is not considered a 9600 Modem and should be avoided.- Talks to other brand V.42 modems at 2400 Baud with LAP-M.

Generic V.32/V.42 (and V.42bis) These modems follow BOTH the CCITT V.32 and V.42 standards for communicating at 9600 bps. - Talks to other brand V.32 modems at 9600 Baud. - Talks to other brand V.42 modems at Top Supported Baud.

Hayes V-Series V.42: The Hayes V-Series V.42 uses the proprietary method of communicating at 9600 Baud but will incorporate the V.42 data compression and error checking - Talks to other V.42 modems at 2400 with error correction/compression. Talks to other MNP modems at 2400 using error correction/compression. Talks to other Hayes V-Series at 9600.

Hayes ULTRA: Uses CCITT V.32 and V.42bis method for communicating at 9600 Baud. Has MNP5 abilities. Has LAP-M abilities - Talks to Other V.32 modems at 9600 Baud Talks to other V.42 modems at up to 9600 Baud Talks to other Hayes V-Series at 9600

Telebit Trailblazer: Uses proprietary PEP method of communicating at 9600 Baud. Has MNP5 abilities. - Talks to other Telebit Trailblazers at 9600. Talks to other MNP modems at 2400 baud with error correction/compression

USR Courier HST DS: The Dual Standard incorporates both the proprietary HST method of communicating at 14400 baud and the and the CCITT V.32 & v.42 methods of communicating at 9600 Baud. (and V.32bis after 1/1/1991) Has MNP5 abilities. - Talks to Other V.32 modems at 9600 Baud. Talks to Other V.32bis modems 14,400 Baud. Talks to Other DS's at 14,400 Baud Talks to 14.4 HST's at 14,400 Baud Talks to old 9600 HST's at 9600 Baud.

COMPUcom Speedmodem/Fax: Uses the Proprietary DIS at 9600 Baud. Has 7200 and 4800 Baud Fallback Has CCITT FAX V.27ter & V.29 Has MNP5 abilities. Has CSP abilities. Talks to Group III Faxs at 9600. -Talks to Speedmodems at 9600. Talks to other MNP modems at 2400 with error correction/compression

No Prices have been stated above this Section, because prices often change,and I want to keep all the prices together so they could be quickly updatedas needed. There are 3 types of prices I will cover. First is The Retail price,second is the Sysop price, which is only available if you run a BBS.

Many Modem Manufactures offer BBS Sysop special prices directly, at about50% off the retail price. First the BBS has to be verified, so the modemmanufacture knows that is is a real BBS that has been running for at least6 Months, and has a minimum number of users, ect. Usually the Manufacturerwill call the BBS once, or twice a few week apart to be sure. Verificationusually take 3-4 weeks. Then the Sysop has to agree to use the Modem on theBBS for some set amount of time.